1. Field of the Invention
The present invention relates to medical devices, e.g. catheters or guidewires commonly used in the placement of catheters, particularly in a patient's vascular system, and particularly to convertible infusion wires that can be used either as a guidewire or a catheter, and, in either case, may be used for infusion of drugs or agents in close proximity with a blood vessel wall or other body cavity during the course of or following an interventional procedure.
2. Description of the Background Art
Medical catheters and guidewires are devices that can be navigated through narrow body passages, typically blood vessels, until the distal end section is in a desired location. Guide wires are typically used for introduction of a catheter over the guide wire. A physician controls the advancement and resulting position of the distal end of the guidewire by manipulations performed at the proximal end outside the body. Then the catheter is advanced over the guidewire, which may be left in place or withdrawn during a procedure using the guidewire.
Catheters generally comprise hollow, flexible tubes that convey fluids, such as contrast agents or pharmacological drugs to or from a desired blood vessel, organ or cavity through an internal catheter lumen. Cardiovascular balloon catheters have an inflatable balloon structure at the distal end for obstructing a blood vessel or, in the case of angioplasty, for expanding an occluded blood vessel.
Cardiovascular guidewires and catheters sometimes have similar structures, but guidewires typically have a solid core and are dimensioned to be received within a catheter lumen. One very common guidewire construction has an elongated, flexible, helical coil having a proximal end and a distal end, the latter being inserted into the patient's vascular system. An internal "core wire" typically extends through the coil lumen with the proximal and distal ends of the core wire attached to the proximal and distal ends of the coil.
In some helical coil guidewires used for cardiovascular purposes, the distal segment of the helical coil is J-shaped to provide improved steerability of the guidewire into various branches of a blood vessel, as shown, for example, in U.S. Pat. No. 5,040,543. A core wire that can be advanced into the coil lumen is provided to adjust the size of the J-shape curve in the distal segment by moving the core wire distally (to straighten out the J) or moving the core wire proximally (to reform the J). The ability to control the J-shape of the distal end increases the facility by which the guidewire can be manipulated to select a desired blood vessel at branch points.
In another application of a guidewire described in U.S. Pat. No. 5,122,136, a "guidewire" is constructed with a coil wire distal segment that may be advanced into an aneurysm and detached to effect thrombosis of the aneurysm cavity. The coil wire distal segment is itself pre-biased to assume a larger coil when released from a straight, surrounding micro-catheter lumen before it is inserted into the micro-catheter lumen and after it is introduced to the site of the aneurysm and advanced out of the lumen. In this configuration and use, the coiled wire distal segment does not function as a guidewire as otherwise described and referred to herein, since it can only be advanced to the site within the lumen of the micro-catheter.
Some guidewires, called "convertible wires" or "infusion guidewires" are constructed of coiled wire defining a guidewire lumen with an outer sheath surrounding or within the coiled wire and are adapted for use both as guidewires and as infusion catheters as disclosed, for example, in U.S. Pat. Nos. 5,178,158, 5,184,627 and 5,211,636. Such convertible wires may be provided with a fixed or removable core wire within the lumen to stiffen it during advancement.
Because of its narrow gauge, flexibility and column strength, the distal portion of a convertible wire can be advanced to a desired site in a blood vessel. Then the physician can advance a catheter over the convertible wire to the site. Depending on the design, the physician can remove the convertible wire from the catheter lumen or leave it in place while conducting a procedure with the catheter. Infusion of drugs or agents is typically effected from the proximal end, through the lumen and out through the distal end lumen opening or through side holes in the sheath or through the spaces between exposed turns of the coiled wire during or following the procedure using the catheter.
Such convertible wires are often employed in conjunction with procedures to temporarily open a blood vessel blockage in order to both provide the guidewire function to introduce a treatment catheter and to also provide infusion at the site of treatment either during or following the treatment.
The acute symptoms of blockage of a vein at a venous valve or a partially sclerosed and narrowed artery may be instigated by the presence of a soft obstruction or blood clot. In the venous and arterial blood vessels, such clots are referred to as an embolus or emboli and a thrombus or thrombi, respectively. Emboli and thrombi are characterized by a soft consistency that maintains a form and is resistant to dissolution in the bloodstream or in water and entraps red blood cells. Recently formed blood clots stabilized in position as emboli and thrombi are soft and jelly-like in consistency and are readily penetrated but reform after the penetrating object is removed. Such blood clots may form for a variety of reasons in the vascular system and be released and flow until they block a partially occluded section of the blood vessel. When this clot blocks a vessel in the leg, for example, the resultant pain or loss of circulation requires its removal or dissolution. When blocking cardiac arteries manifesting atherosclerosis, the resulting ischemic episode triggers the symptoms of chest pain or heart failure, with respect to cardiac arteries, or a stroke or eyesight failure, if the carotid artery or its tributaries are blocked. The invasive removal or dissolution of soft blood clots and the opening of hard obstructions in blood vessels have become commonplace.
To effect the initial opening of a soft obstruction, thrombolytic drugs or clot dissolving agents may be applied through an infusion catheter inserted into the clot to encourage the dissolution of the clot. For example, the infusion catheter disclosed in U.S. Pat. No. 5,085,635 is proposed to be introduced over a guidewire and be used for infusion of thrombolytic drugs (as well as diagnostic agents, in other procedures) out side wall openings into contact with the blood vessel wall. In many instances it may not be necessary to proceed further with a separate procedure to enlarge the blood vessel, if the soft obstruction can be dissolved in situ and the occlusion is not severe.
However, in the use of conventional infusion guidewires, convertible wires or catheters for introducing the dissolving agent, it is not always possible to maintain a concentration of the agent into the soft obstruction pressed against the blood vessel wall, where the infused agent would provide the most benefit. Laminar blood flow through the blood vessel washes the agent downstream before it may have the desired local effect.
Similarly, in other infusion applications following balloon angioplasty or other procedures affecting the blood vessel wall, the laminar blood flow through the vessel washes a drug or agent emitted radially for treatment of the vessel wall downstream before it may have the desired local effect.
In an approach to counter the loss of or more efficiently apply the drug or agent, specialized drug delivery dual balloon catheters have been developed to infuse drugs or agents against the vessel walls through holes in an outer balloon periphery or between two axially displaced, inflated balloons. The dual balloon catheters may have an inner through lumen for perfusion of blood while the balloons are in the inflated position for a matter of hours or days, as described, for example, in U.S. Pat. No. 5,295,962.
In the '635 patent, "pigtail" catheter designs of one or more loops having side wall openings are described, particularly in relation to rapid flush angiography for delivering contrast medium into a heart chamber. Such pigtail catheters are formed with the loop or loops formed in a planar configuration to minimize recoil of the catheter tip during the rapid and high pressure flush of the contrast medium into the heart chamber and blood vessels.
It would be desirable to provide local delivery of lytic agents to a blood clot to magnify their therapeutic effects while minimizing the complications of systemically delivered lytic agents e.g. bleeding. Similarly, it would be desirable to apply and concentrate agents at a blood vessel wall following an angioplasty dilation for treatment of the localized injury to the vessel. Despite the advances and improvements in treatment that have been introduced in recent years, a need remains for an infusion guidewire and catheter that provides a simple and less expensive way to assure delivery of drugs or agents in the low flow rate region adjacent to the blood vessel wall and/or obstructions while allowing perfusion of the blood through the generally central lumen of the blood vessel.